1. Field of the Invention
This invention relates generally to a multicar elevator system having an elevator shaft within which a plurality of independently movable elevator cars operate.
2. Description of the Related Art
In tall buildings, and particularly in tall narrow buildings, a significant portion of floor space is required for elevators. With conventional elevator systems, one elevator car operates in each vertical elevator shaft. One prior art method of reducing the amount of floor space required for such conventional elevator systems includes the use of double-deck elevator cars whereby each elevator shaft contains two attached elevator cars. Such arrangements are shown, for example, in U.S. Pat. Nos. 4,582,173 and 4,632,224. Since the two cars move as a unit, operation thereof is very restricted since only adjacent floors may be simultaneously serviced by the cars. For example, two lobby landings may be employed whereby passengers destined for odd numbered floors must use one lobby and those destined for even numbered floors must use the other lobby. Also, drive motors, hoisting cables, and the like, used to raise and lower the double-deck cars must be of greater power and strength than those needed for use with conventional single elevator cars. Another prior art method of reducing the amount of floor space required for elevators includes use of a pair of elevator shafts in which elevator cars ascend in one shaft and descend in the other. The elevator cars move between elevator shafts adjacent the top and bottom of the vertical elevator shafts. In one such arrangement shown in U.S. Pat. No. 1,458,881, the elevator cars are moved vertically by use of endless chains that extend along the vertical shafts. In U.S. Pat. No. 3,658,155 , a plurality of self-propelled elevator cars are provided which are adapted to travel up one elevator shaft and down another. Each elevator car carries a drive motor connected to a drive member engagable with guide means extending along the elevator shafts and between elevator shafts at the top and bottom of the vertical shafts. The elevator cars are movable laterally from the vertical shafts at any floor for loading and unloading. Since travel is limited to movement in one direction in the two vertical shafts, benefits derived from such arrangements over conventional elevator systems are limited.